This invention is generally related to power converters, and, more particularly, to packaging techniques and heatsink assemblies for improving the thermal performance of a high-density power converter and thereby increase the power density of the converter.
Power converter devices, such as dc/dc power converters, are widely used in numerous applications, e.g., telecommunication and networking applications. A dc/dc converter converts a raw dc voltage (input), usually with a certain variation range, to a dc voltage (output) that meets a given set of specifications.
The most widely used modules are generally provided in certain standard sizes, such as so-called quarter brick, half brick, and full brick. With fast-growing technologies used in the telecommunications equipment, the demands on the output current of the power converters keep increasing so that higher power output can be obtained for a given module size. Thus, increasing the power density of the converter at an affordable cost is a desirable goal of suppliers of power converters, such as the assignee of the present invention. As more components are added to an electronics module to increase its power rating, appropriate distances between circuits positioned at opposite sides of an isolation boundary should be kept to meet safety requirements from agencies such as Underwriters Laboratories. As the actual limit of the usable power of a given module is generally dictated by the thermal-handling capability of its components, thermal management also becomes an important consideration for obtaining optimum performance of power converters.
Traditionally, power modules may be designed using a so-called two-board approach: most heat-generating components are disposed on one metal board, while other components are put on a printed circuit board (PCB), for example, comprising FR4 dielectric, or other suitable material. To reduce the complexity and costs associated with two-board manufacturing operations, a single-board design approach is also used wherein every electrical component, including heat-generating components, are located on a single PCB. Power magnetic circuits, such as power transformers and inductors can also be integrated onto the single PCB. This integration of multiple components on a single PCB presents several challenges to the designer:
One must ensure that safety distances, e.g., creepage and/or clearance distances, are appropriately met for the traces and circuit components on the PCB, as required by safety agencies such as the Underwriters Laboratories Inc. (UL).
One must ensure, through appropriate thermal management of the key power generating components, that the usable power delivered by the converter actually meets its rated specifications.
U.S. Pat. No. 5,990,776, titled “Low Noise Full Integrated Multilayers Magnetic For Power Converters” purports to embed all transformer/inductor windings inside the PCB by not putting any of the transformer/inductor windings on the outside layers of the PCB. Conceptually, safety clearance/creepage requirements should be somewhat reduced and more space should result for mounting other electrical components. Unfortunately, under this approach, it is believed that heat generated by the transformer and/or inductor windings is also trapped inside the PCB, and this may lead to strained thermal performance.